German Patent No. 43 41 796 describes, a pressure sensor arranged in each combustion chamber of the internal combustion engine so that the pressure in the combustion chamber can be detected during a predefinable period of time. In this context, the pressure values during the compression stroke are stored until a predefinable crank angle is reached, and, subsequent to passing the predefinable crank angle, are output again in reversed manner during identical periods of time, allowing a subtraction operation to be performed on the pressure values which continue to be detected during the combustion and the output pressure values detected during the compression stroke. The integral of the determined difference and the appertaining crank angle, at which a predefinable surface portion of the integral is reached, form the bases for determining the deviation of an ascertained crank angle from a predefinable setpoint crank angle, so that, on the basis of the determined deviation, the combustion position (angle) can be regulated.
Furthermore, methods are known in which, for recognizing the specific power stroke, a pressure sensor is arranged in the combustion chamber, and, when a threshold value is exceeded by the sensor signals, it is concluded that the cylinder in question is in the expansion stroke. Moreover, it is known to provide a knock sensor for recognizing the specific power stroke, the sensor signal being compared with a threshold value as well, it being concluded that, when the threshold value is exceeded, the cylinder in question is in its expansion stroke.
The method according to the present invention has the advantage over the known methods that no pressure sensor is provided in the combustion chamber, thus avoiding additional bores in the cylinder head. Moreover, by reconstructing the combustion chamber pressure characteristic from the signal of the knock sensor, it is possible to determine different operating quantities of the internal combustion engine without additional sensors. In this method, consequently, the already existing sensors can be used to regulate different parameters.
It is particularly advantageous that, on the basis of the reconstructed combustion chamber pressure characteristic, an irregular running recognition as well as a misfiring recognition, a determination of the combustion position, and a determination of the phase angle is possible. Consequently, no change needs to be made on the part of the design but the method can be provided simply by adapting the program flow in the control unit accordingly.